DnsResolver is ignoring nameserver from provided url address

### What version of gRPC and what language are you using?
Grpc.Net.Client 2.63.0 and C#

### What operating system (Linux, Windows,...) and version?
MacOs

### What runtime / compiler are you using (e.g. .NET Core SDK version `dotnet --info`)
.NET SDK
Version: 8.0.204
Commit: c338c7548c
Workload version: 8.0.200-manifests.a39c3a9c

### What did you do?
In order to use DNS based address resolution, I configure Address as
`dns://my-dns-server-host:dns-server-port/dns-address-to-be-resolved`

### What did you expect to see?
I was expecting resolver to make DNS query to name server `my-dns-server-host:dns-server-port` and resolve services against `dns-address-to-be-resolved`

### What did you see instead?
But it uses OS configured name servers and ignores `my-dns-server-host:dns-server-port`.

### Anything else we should know about your project / environment?
Looking at Golang implementation of gRPC DNS Resolver and it seems to be correctly implementing the same.

No source files or tests are named. Start by locating the Grpc.Net.Client DNS resolver implementation and compare its handling of the supplied server with the referenced Golang gRPC resolver. Done means a dns:// address queries my-dns-server-host:dns-server-port instead of the OS-configured name servers and resolves dns-address-to-be-resolved.

Written by the indexing model from the issue text.